A communication protocol is a set of rules for data exchange within or between devices. One type of communication protocol is the single edge nibble transmission (SENT) protocol. The SENT protocol is a point-to-point communication protocol for asynchronously and unidirectionally transferring nibbles of data (i.e., 4 bits of data) encoded by pulse width modulation (PWM). The SENT protocol is often applied to automotive applications to transfer high-resolution data from a sensor device to an electronic control unit (ECU) in real time. Such automotive applications include, for example, electronic power steering, throttle position sensing, pedal position sensing, airflow mass sensing, and liquid level sensing applications.
While the SENT protocol is applicable to numerous applications, it has a number of shortcomings that limit its utility. Among these shortcomings is the unidirectional and asynchronous nature of the SENT protocol. Additionally, the SENT protocol is limited to point-to-point communication. To addresses these and other shortcomings, the short PWM code (SPC) protocol can be employed to extend the SENT protocol. The SPC protocol introduces bi-directional, synchronous communication over a signal line shared by two or more devices to thereby improve upon the SENT protocol.
Despite the SPC improvements, the data rate is often still low. A communication system implementing the SPC protocol often has an open and relatively undefined physical layer (i.e., hardware layer). Further, emission control and resistance to electromagnetic injection, as called for by electromagnetic compatibility (EMC) standards, are often managed by filter structures in the physical layer. While the open nature allows for flexibility in designing the physical layer, and the filter structures serve an important role, the open nature and the filter structures also limit the ability of devices to impedance match to the signal line over a wide range of frequencies. This, in turn, limits the attainable data rate.